The present invention relates to a hysteresis device.
In a comparator which compares an input signal with a threshold to output a binarized output signal, when the level of the input signal is varied in the vicinity of the threshold, chattering in which the level of the output signal is varied in a short time is caused. As means for preventing such chattering from occurring, a hysteresis circuit is known. For example, a hysteresis circuit uses two thresholds. The first threshold is indicated by Vref1, the second threshold is indicated by Vref2, and it is assumed that Vref1<Vref2. When the output signal transits from a low level to a high level, the second threshold Vref2 is used, and, when the output signal transits from a high level to a low level, the first threshold Vref1 is used.
Patent Reference 1 discloses a magnetic sensing device in which, from the viewpoint of prevention of chattering, an output signal of a bridge circuit is supplied to a Schmitt trigger circuit which is a kind of hysteresis circuit. Usually, a Schmitt trigger circuit is often configured by an amplifier which is positively fed back by using an operational amplifier, and a Zener diode is often added to an output stage in consideration of stability.    [Patent Reference 1] WO2008/099662
In the case where the above-described bridge circuit detects the existence or non-existence of magnetism, however, it is necessary to provide a Schmitt trigger circuit corresponding to +H of the polarity of the external magnetic field, and another Schmitt trigger circuit corresponding to −H of the polarity of the external magnetic field. Therefore, the circuit has a complicated configuration.
In the case where the Schmitt trigger circuits are operated at a low voltage, the threshold voltages which are adjusted in the Schmitt trigger circuits are very low, and hence there is a problem in that high accuracy is required.